The present invention relates to a gas-liquid separation method for electroconductive gas-liquid two phase flow and the device therefor and, in particular, relates to a separation method for electroconductive gas-liquid and the device therefor suitable for separating and removing the gas phase from gas-liquid two phase flow under a microgravity environment.
Generally, in an analysis device and a separation and purification device relating to bioscience, when gas bubbles are contained in a sample, volume variation becomes sometimes large due to compressibility, and channeling of flow in a flow passage sometimes occurs due to the gas bubbles and the performance of the devices extremely deteriorates. As conventional contermeasures, such as proposed in Japanese Patent Application Laid-Open Nos. 55-121806 (1980) and 62-180711 (1987), were employed devices wherein the flow passage wall and the tube passage were formed by using a hydrophobic porous material having water permeability, flow passages were disposed in a reduced pressure chamber and the gas bubbles contained in the liquid phase were degased. However, in these gas-liquid separation methods, measures were taken such as prolonging the flow passage length for increasing gas separation efficiency and reducing the flow passage cross sectional area for increasing contact area of the gas bubbles with the flow passage wall, so that there arised problems of prolongation of the flow passage length and the increasing flow passage resistance.
Moreover, in a microgravity environment, such as in space, where the effect of separation action with the gravity can not be expected, the separation of the gas-liquid two phase flows is rendered difficult. Further, surface tension is dominant there, so that the combination of the respective bubbles becomes difficult and the contacting area to the gas permeable membrane reduces such that the separation efficiency deteriorates. In such microgravity environment, by forming the flow passage in coils or by disposing swirling vanes in the flow passages, swirling components are provided in the flow of the sample and the gas-liquid two phase flow is separated in many cases by the action of centrifugal force. However, such as in devices relating to bioscience dealing with expensive physiological active material where a sample of trace quantity of flow rate is handled, generation of the swirl components by the flow of sample itself is difficult. On the other hand, in the method of disposing the vane wheel in the flow passage and forcedly generating the swirling components, there exist many problems such as sealing, lubrication and biological contamination.
Examples of separation devices for gas-liquid two phase flows effective under such microgravity environment were proposed in Japanese Patent Application Laid-Open Nos. 58-88012 (1983) and 58-88013 (1983) wherein electrodes in ring shape and the like are disposed along the flow passage of electrical insulation gas-liquid two phase flow, a high electric field region and a low electric field region are formed and the gas phase in the electrical insulation gas-liquid two phase flow is collected.
However, these devices are considered effective for gas-liquid two phase flows having an electrical insulation property; since these devices use a high voltage, there are many of problems with respect to e.g., electrolysis of sample and current leakage when applied to the cases where the electroconductive gas-liquid two phase flows are the subject for separation as in the devices relating to bioscience.